The present invention relates to an exhaust gas control mechanism for a two-stroke engine.
DE-C 464 508 discloses an exhaust gas control mechanism for a two-stroke engine, according to which the exhaust gas muffler is divided into two chambers. The first chamber communicates with the exhaust gas outlet via a large cross-sectional area, while the second chamber communicates with the exhaust outlet via a small cross-sectional area. The entry of exhaust gas into the second chamber is controlled by a valve that is open when the discharge window of the cylinder opens, and then closes as counterpressure builds up in the second chamber, and finally, after reduction of pressure in the second chamber, again opens. This is intended to reduce the operating noise of the two-stroke engine.
Since at the time period of the opened transfer window of the two-stroke engine into the first chamber the discharge window is opened, which adjoins a large outlet cross-sectional area at the exhaust gas outlet, it is not possible to prevent the fresh gases or fuel that enter for the rinsing or flushing to be discharged via the discharge window. Thus, considerable portions of unburned fuel/air mixture can be found in the exhaust gas, which is serious with regard to environmental pollution.
It is therefore an object of the present invention to provide an exhaust gas control mechanism for a two-stroke engine such that the rinsing losses that increase due to the manner of operation are reduced to a minimum.